Atom Transfer Radical Addition to Styrenes with Thiosulfonates Enabled by Synergetic Copper/Photoredox Catalysis

Bifunctionalization of α-Bromophenone: An Access to Functionalized β-Keto Thiosulfones

A simple and high-yielding strategy to produce a variety of β-keto sulfides using asymmetrical and symmetrical thiosulfonates with ketones under mild conditions is reported. It was found that the various substituted compounds, with both electron-withdrawing and electron-donating substituents, afforded a wide range of β-keto thiosulfones (α-thioaryl-β-keto sulfones) in moderate to high yields. The transformations were reliable at the gram-scale, thus illustrating their efficiency and practicality. A plausible mechanism for the protocol is also proposed.

Light-Induced 1,3-Thiosulfonylation of β,γ-Unsaturated Ketones with Thiosulfonates

Sulfur-containing compounds exhibit potent significance in drug molecules. Thiosulfonates as 1,3-thiosulfonylation reactants to olefins have yet to be investigated. Herein, we report photoinduced 1,3-difunctionalization of β,γ-unsaturated ketones with thiosulfonates, which undergo a radical 1,2-acyl shift. The protocol features mild conditions, high regioselectivity, and 100% atom economy.

Electrophotocatalytic Tellurosulfonylation of Alkynes for the Synthesis of β-(Telluro)vinyl Sulfones

Difunctionalization of alkynes has gained a lot of interest in current organic chemistry. Herein, we developed an electrophotocatalytic multicomponent cascade reaction of alkynes and indoles with sulfinic acid sodium salts using elemental tellurium as the tellurium source. Using synergistic anodic oxidation and visible-light irradiation, various β-(telluro)vinyl sulfones have been prepared. This strategy features mild reaction conditions, excellent substrate scope, readily available starting materials, and great functional group tolerance.

Visible-Light-Driven Unsymmetric gem-Difunctionalization of Vinyl Azides with Thiosulfonates or Selenosulfonates

Thiosulfonylation and selenosulfonylation of vinyl azides with thiosulfonates and selenosulfonates were achieved using Cu(dap)2Cl as a photosensitizer under visible-light irradiation. This reaction is the application of a vinyl azide substrate in a group transfer radical addition (GTRA) reaction, through β-difunctionalization, to obtain a variety of unsymmetric difunctionalized N-unprotected enamines.

Synergistic Photoredox and Iron Catalyzed 1,2-Thiosulfonylation of Alkenes with Thiophenols and Sulfonyl Chlorides

Herein, a three-component 1,2-thiosulfonylation of alkenes with thiophenols and sulfonyl chlorides via synergistic photoredox and iron catalysis is described. Compared with previous studies, this protocol avoids tedious pre-synthesis of thiosulfonates and employs more readily accessible sulfonyl chlorides as a sulfonation reagent. Moreover, the reaction exhibits high compatibility with styrenes and unactivated alkenes as well as diverse sulfonyl chlorides, especially sulfamoyl chlorides. Preliminary mechanism investigations reveal that a radical pathway is involved in the catalytic cycle.

Simultaneous Preparation of Sulfides/Selenides and Sulfones via Synergistic Nickel-Catalyzed Reductive Coupling and SN2 Reaction

Sulfone compounds and thioether compounds are two highly valuable classes of compounds, but it is challenging to prepare sulfone and thioether compounds simultaneously and efficiently. Here we report that sulfides/selenides and sulfones can be obtained simultaneously using allyl bromide/benzyl bromide-activated alkyl bromides and thiosulfonates/selenosulfonates using a nickel-catalyzed reductive coupling and SN2 synergistic strategy, which is characterized by excellent atom and step economy, mild reaction conditions, broad functional group compatibility, and excellent yields.

Photocatalytic C(sp3)-H thiolation by a double SH2 strategy using thiosulfonates

Site-selective C(sp3)-H thiolation using thiosulfonates has been achieved using the decatungstate anion as a photocatalyst. Using the protocol, a variety of thiolated compounds were synthesized in good yields. The transformation consists of a cascade of double SH2 reactions, HAT and ArS group transfer, and PCET (proton-coupled electron transfer) of the leaving arylsulfonyl radical to arylsulfinic acid thus allowing the catalyst, W10O324-, to be recovered.

Syn-Selective Chlorosulfonylation of Alkynes via a Copper-Powder-Initiated Atom Transfer Radical Addition Reaction and Mechanistic Studies

Copper-powder-catalyzed syn-selective chlorosulfonylation of readily available alkynes by an atom transfer radical addition (ATAR) process has been developed, providing straightforward access to a broad range of (Z)-β-chlorovinylsulfones in good yields under mild conditions. In addition, this method is ligand-free and features excellent stereoselectivity and high atom economy. Moreover, the product was obtained without an apparent loss of yield when the reaction was performed on the gram scale at a low catalyst loading. In this reaction, the copper powder not only acts as a sulfone radical initiator but also produces the catalytically active CuCl species. Mechanistic investigations and DFT calculation studies revealed that the stereoselectivity is controlled by the thermodynamic stabilities of the in situ-generated cyclic alkenyl Cu^II complex intermediate, which can serve as a chlorine atom transfer agent.

External oxidant-free and selective thiofunctionalization of alkenes enabled by photoredox-neutral catalysis

A photoredox approach was reported to realize a highly selective three-component thiohydroxylation, thioalkoxylation and thioamination of vinylarenes towards valuable vicinal S,O- and S,N-disubstituted molecules under mild conditions.

Visible-Light-Induced Radical Cascade Reaction of 1-Allyl-2-ethynylbenzoimidazoles with Thiosulfonates to Assemble Thiosulfonylated Pyrrolo[1,2-a]benzimidazoles

A visible-light-induced radical domino reaction of 1-allyl-2-ethynylbenzoimidazoles with thiosulfonates was developed, which generated the thiosulfonylated pyrrolo[1,2-a]benzimidazoles in moderate to good yields. This reaction proceeded under transition-metal-free conditions with good functional group tolerance and high regioselectivity. The possible pathway involved thiosulfonates were activated through the energy transfer route promoted by photocatalysis.